A TreeView/TreeMenu-like control would be great to have. Currently there is no easy way to realize tree-like structures, like the menu that the official Mail App has.

Provide a universal JumpList similar to the Windows Phone JumpList.

Port the Windows Phone ImageEditor to WinRT.

http://www.telerik.com/products/windows-phone/overview/all-controls/image-editor.aspx

Implement Scheduler control

Port RadWindow control to Windows Universal

A DataStorage that can be used for both in Windows 8.1 and Windows Phone 8.1 apps.

Add the ability to display hierarchical content within the DataGrid

I think that will be a very good feature. Just create a gantt control available over this platform. A gantt control like UI for Silverlight will be a fantastic one.

Ability to view and print report documents

A color picker that can be used for both in Windows 8.1 and Windows Phone 8.1 apps.

Provide a tabstrip control that allows users to display content on tabs.

 - Tab content could use virtualization to avoid extra rendering
 - Follow themes from Telerik
 

A docking control similar to what is available in UI for Silverlight.

I've ported over my app from Windows Phone 7/8, but now I've found myself at a loss of functionality without your textboxes available as universal controls. RadTextBox, RadPasswordBox, and RadNumericUpDown are all controls that would be fantastic if they could be ported over to Universal.

Thanks!

Make the Grid universal.

Make RadDiagnostics Universal control.

The RichTextEdit from Microsoft is still not a perfect port, and missing many functionality.

And only a few .NET vendor that has RichTextEdit control in their Windows Phone+WindowsRT suite, Telerik unfortunately not included, :(

Please reclaim your crown as most complete Windows Store Suite back by adding RichTextEdit control for Windows Universal.

Universal barcode.